The present invention relates in general to the field of electrical power distribution systems. More particularly, the present invention relates to power switching control devices as used in electrical power distribution systems.
A common problem in almost any electrical power distribution system is a momentary disruption of electrical service or faults, such as might be caused by a momentary short circuit. Most of these faults are self correcting and do not require permanent fuse or circuit breaker protection because they terminate quickly. If a fuse should burn out or a circuit breaker should trip, however, the power line would be open and customers would be deprived of their electrical power. Service calls to replace fuses or reset circuit breakers would then be required, thus escalating the customer""s costs.
A power switching device system is a fault-interrupting device used to sense current, voltage, and/or frequency variations and isolate faulted portions of distribution feeders thereby protecting power lines in an electrical power distribution system. More particularly, power switching device systems. generally, include a power switching device and a power switching control device. The power switching device may be an electromechanical device, similar to a circuit breaker that includes a magnetic actuator or magnetic latch for opening and closing each line of a power system.
A magnetic actuator may a solenoid that magnetically latches when energized with the proper polarity of direct current (DC). One type of magnetic actuator is the single-coil design. To operate a single-coil magnetic actuator, the current flows in one direction for a latch (close) function and in the opposite direction for the unlatch (open) function. Each power switching device has three magnetic actuators (one for each phase of AC power) and each magnetic actuator is mechanically connected to a vacuum switch. Presently, each magnetic actuator requires about 20 amps to complete a latch (close) operation and about 10 amps to release.
When a power switching control device senses a fault condition in a power line, the power switching control device opens the magnetic actuator. By opening the magnetic actuator, the power switching device interrupts the power flow to the remaining portion of the distribution system, i.e. clears the fault from the remaining portion of the system.
If the fault has not cleared itself during a fixed time interval, then, as the name suggests, the power switching control device will reclose the magnetic actuator, and if the fault condition has been cleared, power service will resume. If, however, the fault condition has not been cleared, the power switching device will again trip open the magnetic actuator after a second fixed time interval. If, after a predetermined number of reclose operations, and the fault condition has not been cleared, the power switching control device will permanently lockout the magnetic actuator permanently open the circuit). The circuit then remains open until the system is repaired and/or the fault condition is eliminated. An exemplary power switching device for use with the present invention is the VR-3S recloser manufactured and distributed by ABB Power TandD Company, Inc., Raleigh, N.C.
A power switching device is operated by a power switching control device (controller). Typically, the controller is an electronic control circuit that provides the intelligence that enables a power switching device to sense overcurrents, select timing operations, and time the reclosing functions. The controller is a microprocessor-based device that includes software and hardware components for controlling the operation of the power switching device. The hardware, or physical elements, are the integrated circuits, resistors, capacitors, displays, switches, and so forth. The software is the coded instructions that the microprocessor uses to control the power switching device.
A conventional controller contains various components. For example, a power supply is typically provided in a controller and provides power to other components of the controller. A voltage regulator may also be used in a controller to provide a stabilized input signal to various components in the controller. Storage or memory may also be provided for temporarily and/or permanently storing data and/or software for the controller. For use with a power switching device, for example, this data would include line current magnitudes and command information such as multiple time-current characteristic curves and protection setting groups. The memory can be random access memory (RAM) or read only memory (ROM) or any other type of memory. ROM is preferably electrically programmable for easy modification and is used for storing programming information. The storage can be internal to the controller or external to the controller.
A controller may also include a display for displaying information and a keyboard or other input device may be used for entering information. Indicator lamps provide status information such as power switching device open, power switching device closed, control lock out, above minimum trip, malfunction and lock in, An exemplary controller unit is the PCD2000 manufactured and distributed by ABB Power TandD Company, Inc., Raleigh, N.C.
Typically, a controller controls (e.g. opens and closes) the position of magnetic actuator in a power switching device by applying a voltage across the coils in the magnetic actuator. As such, when a certain amount of voltage is applied, the actuator will open or close, thus opening or closing an associated power line. However, such a method of opening and closing a magnetic actuator oftentimes wastes energy and does not provide the ability to control the speed at which the actuators open or close. Therefore, a need exists for power switching control device that efficiently and effectively controls a magnetic actuator in a power switching device.
The present invention satisfies the aforementioned need by providing a power switching control device and methods for using the same to control a magnetic actuator within a power switching device using a series of modulated current pulses. In one embodiment of the present invention, the modulated current pulses are tunable and, as such, enables the control device to be compatible with multiple types of actuators each having various impedance characteristics. Also, a power switching control device in accordance with the present invention may control the speed at which the magnetic actuator opens and closes.
According to one embodiment of the present invention, a method is provided for controlling a magnetic actuator within a power switching device including a magnetic actuator having a coil and an armature. In this manner, a series of modulated current pulses is applied through the coil of the magnetic actuator in a first direction such that the actuator moves from a first position to a second position and a series of modulated current pulses is applied through the coil of the magnetic actuator in a second direction such that the actuator moves from the second position to the first position.
In one embodiment of the present invention, certain operating characteristics of a power switching device can be ascertained by analyzing the impedance of the magnetic actuator coil within the power switching device. As such, the position of the magnetic actuator may be determined within the power switching device. Alternatively, in another embodiment of the present invention, the physical condition of the magnetic actuator coil is determined.
Additionally and in another embodiment of the present invention, a power switching device control device is provided having an improved energy management system therein. In this manner, the controller includes a voltage regulator that has the ability to switch between operating modes.